Pediatricians have been telling day care centers for years that there's no medical reason to send kids home because of mild sniffles, a touch of a fever or even after a single instance of vomiting.

Ring worm may be a closer call, but a small circular rash when kids are otherwise in good spirits isn't reason enough for them to stay home either.

Still, researchers found the majority of day care centers they tested with a quiz of five scenarios like these would have kept 57 percent of kids home unnecessarily.That puts a burden on parents and is occurring despite national guidelines, which have also been endorsed by some states.

If the children have shown symptoms, they've already been contagious and have "done the damage," study author Dr. Andrew N. Hashikawa of the Medical College of Wisconsin in Milwaukee told Reuters Health. "It doesn't do any good to send these kids home."

The results, just published online by the journal Pediatrics, come from a survey of day care centers in Wisconsin.

Bigger day care centers were slightly less likely than smaller ones to send kids with mild symptoms home. The researchers suspect the difference could be due to more staff and also more space to segregate sick kids.

But everybody working in day care seems to need a little better training on how to make the cut on which kids are sick enough to go home and which one are OK to stay.

Shots is the online channel for health stories from the NPR Science Desk. We report on news that can make a difference for your health and show how policy shapes our health choices. Look to Shots for the latest on research and medical treatments, as well as the business side of health. Your hosts are Scott Hensley and Nancy Shute. You can reach the Shots team via our contact form.